1. Field of the Invention
The present invention relates generally to a sintered nickel electrode for alkaline storage battery formed by filling nickel hydroxide as an active material into a porous sintered substrate, method of forming the same, and an alkaline storage battery using as its positive electrode such sintered nickel electrode for alkaline storage battery, and is particularly characterized in that the above-mentioned sintered nickel electrode for alkaline storage battery is modified to improve charge characteristic under high temperature conditions, thus to stably attain a high discharge capacity in the alkaline storage battery using as its positive electrode such sintered nickel electrode for alkaline storage battery.
2. Description of the Related Art
In alkaline storage batteries including a nickel-metal hydride battery, nickel-cadmium battery, and the like, a sintered nickel electrode for alkaline storage battery has been used as its positive electrode.
The sintered nickel electrode for alkaline storage battery has been formed by chemically impregnating a porous sintered substrate which is obtained by sintering with salt as an active material, and then filling nickel hydroxide as the active material into the sintered substrate. Such nickel electrode for alkaline storage battery is superior in charge/discharge characteristic at high electric current because conductivity of the sintered substrate is high and close adherence between the active material and the sintered substrate is high.
However, there have remained problems that when the alkaline storage battery using as its positive electrode the above-mentioned sintered nickel electrode for alkaline storage battery is charged under high temperature conditions, an oxygen evolution overvoltage of the positive electrode is decreased, thus in addition to a charge reactivity in which the nickel hydroxide is oxidized to nickel oxyhydroxide, an oxygen evolution reaction as a side reaction occurs, thus a sufficient discharge capacity is not attained, and hence charge characteristic under high temperature conditions is degraded.